The present invention relates generally to a pilot operated rotary valve and in particular to a pilot operated rotary valve which can be turned to an "on" or "off" position with an increase in hydraulic pressure in a single hydraulic flow line. The novel valve will select and operate one or more resiliently biased, two position actuator(s) as a result of alternate cycles of hydraulic pressurization and depressurization of a single inlet line supplied from an external pressure control source.
There are many applications in the prior art where it is necessary to operate a hydraulic actuator with only one hydraulic line, and, in some cases, pressure is required to be maintained in that line in order to hold the actuator in the required position. Such case may occur where there is no opportunity to have a manually operated shut-off valve because of lack of space or access.
For instance, continuous mining machines have a rotatable mining head with an elongated shaft carrying a plurality of laterally spaced rotatable cutter support members. An outer cutter support member is mounted on each end of the shaft in a fluid tight relationship and each is extensibly and retractably movable axially on the shaft away from and towards the center of the mining head to thereby change the width of the mining head. Each of the outer support members is resiliently biased to the innermost position on the shaft and a single fluid channel extends axially through the shaft for supplying hydraulic fluid from a pressure source to the interior of each of the outer support members to extend them outwardly. Thus when the machine is cutting in a seam of coal or ore, lo pressure is supplied through the fluid channel which forces the outer support members to their extended positions. As long as the machine is cutting or mining material, the fluid pressure is maintained in the fluid channel to keep the outer support members in their extended position. When it is necessary to move the mining machine back from the mining face, it is necessary to remove the fluid pressure to allow the outer cutter support members to return to their innermost positions by means of biasing springs thereby providing clearance on each end of the cutting head which will allow the machine to be maneuvered from its final cutting position.
This system uses high pressure seals about the rotating shaft so that hydraulic fluid can be coupled externally of the rotating shaft to the fluid channels which are formed on the inside of the shaft and extend axially through the shaft for supplying the hydraulic fluid to the interior of each of the outer support members. Once the pressure has been applied with such a force as to extend the outer cutter support members, that pressure must be maintained until the cutting is completed and then the outer cutter support members can be retracted. This creates a sustained pressure on the seals about the rotating shaft which carries the cutter heads. This sustained pressure causes the seals to wear rapidly. Since they are expensive and time consuming to replace it would be advantageous to find means for enabling the outer cutter support members to be maintained in the extended position with the pressure removed from the seals until such time that it is necessary to retract the outer cutter support heads. Since only one hydraulic flow line can be accommodated through the seals, any attempt to place a normal pilot operated valve between the seals and the outer support members can be disregarded. Further, a manually operated valve could not be operated under such conditions because there is no access to it.
The hydraulic device of the present invention is a pilot operated, stepping, directional valve which will select and operate one or more resiliently biased, two position actuator(s) as a result of alternate cycles of hydraulic pressurization and depressurization of a single inlet line, supplied from an external pressure control source.
This device will permit hydraulic flow directly to the outlet(s) anytime the inlet is pressurized. Thus, the first cycle will extend the actuator and, at the same time, close the directional valve to block the fluid flow from the actuator to the inlet line thus keeping the actuator(s) extended. The next cycle of pressurization will open the valve between the inlet and outlet(s) and the valve will remain open during the depressurization part of the cycle, allowing the trapped fluid volume in the actuators to return through the inlet to the single hydraulic line to the source thus allowing the resiliently biased actuator(s) to return to the retracted position.
Thus, the present valve circuit permits depressurization of a single inlet line while maintaining pressure on the outlet which in-turn traps the fluid volume necessary to maintain extension of the actuator(s). This unique feature relieves internal system components in the supply pressure line of high pressure (such as rotary junction seals) while keeping the actuator(s) extended. As stated, this valve allows the operation of one or more resiliently (spring) biased hydraulic actuators by using a single hydraulic pressure line. It is applied primarily where the supply line, from the hydraulic pressure source to the actuators, must traverse through a rotating section where multiple fluid passages would normally require complex drillings and elaborate concentric rotary seals. An example would be the extendable cutter ends of a continuous mining machine with a rotating cutter drum.
Thus it is an object of the present invention to provide a piloted rotary "on-off" valve which will couple hydraulic fluid from a valve input to a valve output in the "on" position and then move to the "off" position where it will stay, thereby retaining the fluid volume on the down stream side while enabling the pressure on the upstream side to be removed. With a successive increase in pressure on the upstream side, the rotary valve will then index once again to the "on" position thus opening the valve to enable the fluid volume and pressure on the downstream side to be relieved with the successive decrease of upstream hydraulic pressure.
It is also an object of the present invention to provide apparatus for extending, holding and enabling retraction of a hydraulic actuator using only a single pressurizable hydraulic fluid line without maintaining the pressure in the hydraulic fluid line while holding the actuator in this extended position.
It is still another object of the present invention to provide a two-way valve which is driven to a different position, either open or closed, each time the single hydraulic line is pressurized thereby affecting either extension or retraction of a hydraulic device coupled thereto.
It is yet another object of the present invention to utilize the piloted rotating valve in a continuous mining machine with a single hydraulic line wherein a two-way valve is driven to a different position, either open or closed, to affect extension or retraction of the outer cutter head support members. Extension of the outer support members is maintained and the internal fluid pressure released from the seals until a retraction of the outer support members is desired. A repressurization of the hydraulic line changes the valve position to the "on" position and when the hydraulic pressure is removed, the position of the extended auger is reversed by a spring or other resilient bias means which returns it to the retracted position.